Furnace for converting hydrocarbons



H. E. CHARLTON FURNACE FOR C'ONVERTING HYDROCARBONS 2 SHEETS-SHEET l Nov. 6, 1951 Filed April 5, 1949 Nov. 6, 1951 H. E@ CHARLTON 2,574,088l

FURNACE FOR coNvERTING HYDRocARBoNs Filed Apr-11 5, 1949 A 2 SHEETS- SHEET 2 ,4 Horne vs Patented Nov. 6, 1951 FURNACE FOR CONVERTING HYDRO- CARBONS Henry Ernest Charlton, Ashton-on-Mersey, England, assigner to Petrocarbon Limited, London,

England Application April 5, 1949, serial No. 85,615 In Great Britain April 12, 1948 3 claims. (01.235277) This invention relates to the conversion of hydrocarbons by thermal treatment and includes conversions which take place in the presence or in the absence of a catalyst'.

More particularly the invention relates to the carrying out of conversions of hydrocarbons of the' kind comprising two consecutive reaction stages of differing heat requirements, the first stage being endothermic' and requiring a large heat input, and the second stage being substantially thermo-neutral, or slightly exothermic and requiring no substantial heat input.

Examples of conversions of this kind are the conversions of hydrocarbons which are wholly or mainly non-aromatic substantially completely into olefin-containing gases and aromatic hydrocarbons. Such conversions are referred to in I J.` K. Patent No. 575,383 and consist essentially of a cracking reaction followed by an arcmatisation reaction though the two reactions may overlap to some extent. The cracking reaction requires a large and rapid heat input whilst the aromatisation reaction requires no substantial heat input.

In accordance with the invention a method of, or process for, carrying out conversions of hydrocarbons of the kind referred to above, comprises passing the hydrocarbon starting material in uid form through a number of reactors which pass through a furnace heated by one or more fluid fuel burners firing into or by hot gases entering that end of the furnace at which the hydrocarbon fluid is introduced into the reactors, the hot gases produced by the burneror burners or introduced into the furnace passing through the furnace in the same direction as the hydrocarbon fluid to leave through a flue at the other or outlet end of the furnace, a cooling blanket of gases being introduced into that part of the furnace between its ends corresponding to the position at which the conversion taking place in the reactors passes from the endothermic stage into the thermo-neutral or slightly exothermic stage.

- The fl'ring of the furnace is regulated so as to provide the heat required for the rst endothermic stage of the conversion and the temperature and quantity of the cooling gases are such as `to reduce the temperature in the succeeding part of the furnace to that required by the second stage of the conversion and to maintain this temperature in the succeeding part of the furnace.`

All the gases introduced leave the furnace 'through the iiue at the exit end.

The cooling gases may comprise a vportion of the flue gases which have left the furnace and have been cooled, as will generally be found necessary, by r,performing an additional heating operation which may, for example, consist of, or include theV vapourising or pre-heating of the fluid'fed to the reactor.

' yThe apparatus in accordance with the invention for carrying out conversions of hydrocarbons of the kind referred to, comprises a furnace through which one or more reactors pass, ring means at the inlet end of the furnace providing hot gases which pass through the furnace, an outlet for the gases at the other or outlet end of the furnace and means for introducing a blanket of Agases into the furnace between its two ends.

The means for introducing a blanket of gases into the furnace may comprise a duct surrounding the furnace and lprovided with jets protruding into the furnace. Means may also be provided for circulating part of the flue gases leaving the furnace to this duct. It will generally be found necessary to cool the gases before recirculation to the furnace and this is preferably done by passing them over preheaters or vapourisers for the charging stock mounted in a chamber close to the furnace. Additional cooling, if required, may be carried out by passing the gases over a waste heat boiler.

The reactors used in carrying out the invention preferably comprise an initial portion of relatively high surface to volume ratio designed for the carrying out of the endothermic reaction stage and a following portion of relatively low surface to Volume 'ratio designed for the carrying out of the thermo-neutral or exothermic reaction" stage, as described in British Patent No. 575,383. Thus, for example, in applying the invention to the conversion of petroleum fractions into olefin-containing gases and aromatic hydrocarbons the reactor may consist of a tube of 3 inches diameter expanding into a tube of 10 inches diameter.

One method of carrying out the invention as applied to the conversion of hydrocarbons which are wholly or mainly non-aromatic, substantially completely'into olefin-containing gases and aromatic hydrocarbons will be described below with Vreference to the accompanying drawings in prises a vertical furnace l0' of rectangular cross- 2,574,088 l ,y l

3 section having a number of gas burners II ring into the furnace along the major axis of the top of the furnace and an exit flue I2 along the centre of the bottom of the furnace to which the gaseous products of combustion pass through slots I3. A number of tubular reactors I4 (only two of which are shown in Fig. l) are arranged along'feachfof the longer sides of the furnace I0. Each reactor I4 comprises a relatively narrow tube I5 of 3 inches diameter passing into a relatively wide tube IB of 10 inches diameter, the narrow Apart I5 of the reactor being designed for carrying out the cracking stage of the conversion which is endothermic and the wider part I6oi the tube being designed for carrying out the aromatisation stage of the conversion which is thermo-neutral, or slightly exothermic.

Surrounding the furnace I at that which the narrow part I of the reactor .I4 enters the wider part I6 is a duct Il provided with a series of jets I8, I9 protruding into the furnace, a number of jets -I8 being arranged along the upper part of the duct Il and a number of jets I9 being arranged along the lower part of the duct I'I and in staggered relationship to the upper jets I8. Adjacent to the furnace is a chamber containing a number of vapouriser coils 2I, each of which is connected to the top of a reactor I4 at one end through a feed pipe 38 `and to Aa common source of liquid hydrocarbon at the other end through a feed pipe 39. The Yfeed pipes 38 connecting the vapourisers `2| to the reactors I4 pass vthrough ducts 4.0 and 4I 'along each side of the top of the furnace I0. Each reactor I4 is provided at its lower end with an outlet .pipe 42 feeding through a valve 43 into a common offtake pipe 44. Means 45 are provided for quenching the products leaving the Vreactors I4. The exit fiue I2 below the bottom of furnace I0 communicates with a duct 212 which is in communication with chamber 20, the flue gases passing into duct 22 and over the wall 23 into chamber '20. Below chamber 20 is a chamber 24 in which a low pressure steam boiler 25 may be mounted.

On both sides of the chambers "20 and 24 are mounted a series of ducts 26, 121, 28, 29 and 30, the last of which communicates Vthrough duct 3l with fan 32 for circulating gases through duct 33 into duct l1. Dampers 34, 35 and 36 arenprovided for controlling the flow of gases from fiue I2. This system of ducts, dampers and fan are provided on both sides of the chambers 20 ,and 24 though only one system is shown in the drawings.

With the dampers all shut the gases from flue I2 flow up duct 22 over wall 23 through chamber 20, passing over the vapourising coils 2|, through chamber 24, passing over the steam Vboiler I25, and thence out through the duct 31 tothe main stack.

By opening damper 35 tothe required degree, the desired quantity of thegases leaving chamber 24 may-be drawn through ducts 29,30 and 31| to the fan 32 and passed via duct 33 Vinto ,duct I1 and distributed through jets I3 and I9 .into the furnace. By opening damper '36 to the required degree, the desired quantity .of the gases leaving chamber 2l) may be made to by-,pass chamber 24 and are passed direct to the fan 32 through ducts 28, 30 and 3I. By opening damper 34 to the required degree, the desired quantity of the gases coming from flue I2 are caused vto bypass the chamber 20 and pass instead through ducts 26, A2`I to the chamber 24 and thence, as determined by the position kof damper 35, .to the fan 32 or duct 31 or to both.

level Vat By means of the duct and damper system d-' scribed above accurate control of the quantity and the temperature of the cooling gases distributed into the furnace through the jets Il, I9 is obtained.

The furnace may be fired by oil burners in place "of the gas burners referred to above.

The vapour phase conversion at 650 to 750 C. of a non-aromatic petroleum naphtha or kerosene into olefin-containing gases and aromatic hydrocarbons, is carried out in the apparatus described above in the following manner. The charging stock is fed from a liquid container through the feed pipes 39 to the vapourisers 20, in which it is'vapourised and superheated and then fed through the feed pipes 38 into the reactors I4,

Vwhich may be packed with the metallic hydrogenation and dehydrogenation catalyst referred to in British Patent No. 552,216 or with bodies formed of a vitreous ceramic, refractory material such as hard porcelain as described in patent application No. 85,726 filed in the United VStates on April 5, 1949.

The charging stock is passed through the reactors at a pressure up to about 5, and preferably between 1 and 3, atmospheres gauge pressure and with a space velocity between 0.05 and 0.6 and preferably between 0.2 and 0.6, litres (as liquid) of charging stock per hour per litre of reactor volume.

, The products leaving the reactors I4 pass. after quenching by means 45, through the youtlet pipes 42 into the off-take pipe 44.

The furnace is fired by the gas burners ,|.I .arranged along the top to give a temperature of about 800 to 900 C. at the top end of the furnace, this temperature gradually falling to about :'150 to 800 C. just above the level of the duct. The top parts of the reactors are heated mainly .by radiation from the gas flames.

A cooling blanket of gases at a temperature of 300 to 400 C. Ais introduced from the duct ,I'I into the furnace through .the jets I8, I3 so Yas to ,reduce the furnace temperature to aboutr700 .C. and this temperature is maintained down to the bottom of the furnace, the waste gases vpassing through the slots I3 into the flue I2 and thence are partly passed to the stack and Iare partly recirculated to the duct I1, after first passing through one or the other or both of chambers 20 and 24.

Though the apparatus has been described-with reference to straight tubular reactors, it may ybe used with other forms of reactors, for example. both the rst and second ,parts of each reactor may consist of coils but it is essential thatithe first part should be located in the earlierpart of the furnace from the firing po'int to the level o! the duct and the second part of the reactor should be located in the .succeeding part ofthe furnace from the duct level to the exit ue.

I claim:

l. An apparatus for converting non-aromatic hydrocarbons into olefin-containingr gases fand aromatic hydrocarbons which comprises a single chamber furnace, a plurality of straight tubular reactors extending vfrom one end to a second/'end stituting a cracking yzone and ,said secondportion ,an aiomatization zone,A means to feed said hydrocarbons to said firsti portion of said tubes adjacent the rst end of said furnace, means to remove products from said second portion of said tubes adjacent the second end of said furnace, means to supply hot gases positioned within said furnace adjacent the first end thereof, exhaust means for said gases communicating with the interior of said furnace adjacent said second end thereof, and means for introducing cooling gases communicating With the interior 0f said furnace intermediate the ends thereof and adjacent said point of juncture of said tube portions so that said hydrocarbons are heated to a relatively high temperature and supplied with suicient heat to maintain an endothermic cracking reaction in said cracking zone and are only supplied with sufficient heat to maintain stable temperature conditions in said aromatization zone.

2. An apparatus for the conversion of nonaromatic hydrocarbons into Glenn-containing gases and aromatic hydrocarbons which comprises a furnace having a relatively unobstructed firing chamber of substantially rectangular crosssection, a number of burners arranged along the major axis -at one end of said chamber, a ue outlet-at the other end of said chamber, a plurality of straight tubular reactor tubes arranged along the side walls of the chamber on each side of the burners and extending from the one end to the other end of the chamber, each of said reactors comprising a rst portion of relatively small cross-section commencing at the said one end of the chamber and merging into a following portion 0f relatively large cross-section ending at the said other end of the chamber, means for intro# ducing cooling gases into the interior of the chamber at about a plane passing through the points of merger of the said initial portions and said following portions of the reactors, means to feed said non-aromatic hydrocarbonsto said reactor tubes adjacent the one end thereof and means to remove products adjacent lche other end thereof so that the hydrocarbons passing through the said reactor tubes now in concurrent relation to the gases produced by said burners.

3. The apparatus of claim 1 wherein the means for introducing cooling gases comprises a duct positioned about the furnace intermediate the ends thereof and provided with a plurality of staggered jets communicating with the interior of the furnace.

HENRY ERNEST CHARLTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,860,838 Leslie May 31, 1932 1,972,099 Lientz Sept. 4, 1934 1,976,717 Dunstan et al. Oct. 16, 1934 2,101,485 Youker Dec.' 7, 1937 2,114,544 Seguy Apr. 19, 1938 2,147,399 Borden g Feb. 14, 1939 FOREIGN PATENTS Number Country Date 575,383 Great Britain Feb. 15, 1946 

1. AN APPARATUS FOR CONVERTING NON-AROMATIC HYDROCARBONS INTO OLEFIN-CONTAINING GASES AND AROMATIC HYDROCARBONS WHICH COMPRISES A SINGLE CHAMBER FURNACE, A PLURALITY OF STRAIGHT TUBULAR REACTORS EXTENDING FROM ONE END TO A SECOND END OF SAID FURNACE, EACH OF SAID REACTORS COMPRISING A STRAIGHT INTEGRAL TUBE INCLUDING A FIRST PORTION OF RELATIVELY SMALL DIAMETER EXTENDING FROM SAID FIRST END OF SAID FURNACE TO A POINT OF JUNCTURE WITH A SECOND PORTION OF RELATIVELY LARGE DIAMETER EXTENDING FROM SAID TO A POINT OF JUNCTURE SECOND END OF SAID FURNACE, SAID FIRST PORTION CONSTITUTING A CRACKING ZONE AND SAID SECOND PORTION AN AROMATIZATION ZONE, MEANS TO FEED SAID HYDROCARBONS TO SAID FIRST PORTION OF SAID TUBES ADJACENT THE FIRST END OF SAID FURNACE, MEANS TO REMOVE PRODUCTS FROM SAID SECOND PORTION OF SAID TUBES ADJACENT THE SECOND END OF SAID FURNACE, MEANS TO SUPPLY HOT GASES POSITIONED WITHIN SAID FURNACE ADJACENT THE FIRST END THEREOF, EXHAUST MEANS FOR SAID GASES COMMUNICATING WITH THE INTERIOR OF SAID FURNACE ADJACENT SAID SECOND END THEREOF, AND MEANS FOR INTRODUCING COOLING GASES COMMUNICATING WITH THE INTERIOR OF SAID FURNACE INTERMEDIATE THE ENDS THEREOF AND ADJACENT SAID POINT OF JUNCTURE OF SAID TUBE PORTIONS SO THAT SAID HYDROCARBONS ARE HEATED TO A RELATIVELY HIGH TEMPERATURE AND SUPPLIED WITH SUFFICIENT HEAT TO MAINTAIN AN ENDOTHERMIC CRACKING REACTION IN SAID CRACKING ZONE AND ARE ONLY SUPPLIED WITH SUFFICIENT HEAT TO MAINTAIN STABLE TEMPERATURE CONDITIONS IN SAID AROMATIZATION ZONE. 